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The fine-scale structure of Long Beach, California, and its impact on ground motion acceleration

Castellanos, Jorge C. and Clayton, Robert W. (2021) The fine-scale structure of Long Beach, California, and its impact on ground motion acceleration. . (Unpublished) https://resolver.caltech.edu/CaltechAUTHORS:20211012-211827814

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Abstract

The metropolitan Los Angeles region represents a zone of high-seismic risk due to its proximity to several fault systems, including the San Andreas fault. Adding to this problem is the fact that Los Angeles and its surrounding cities are built on top of soft sediments that tend to trap and amplify seismic waves generated by earthquakes. In this study, we use three dense petroleum industry surveys deployed in a 16x16-km area at Long Beach, California, to produce a high-resolution model of the top kilometer of the crust and investigate the influence of its structural variations on the amplification of seismic waves. Our velocity estimates reveal substantial lateral contrasts and correlate remarkably well with the geological background of the area, illuminating features such as the Newport-Inglewood fault, the Silverado aquifer, and the San Gabriel river. We then use computational modeling to show that the presence of these small-scale structures have a clear impact on the intensity of the expected shaking, and can cause ground-motion motion acceleration to change by several factors over a sub-kilometer horizontal scale. These results shed light onto the scale of variations that can be expected in this type of tectonic settings and highlight the importance of resolution in modern-day seismic hazard estimates.


Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/essoar.10507964.2DOIDiscussion Paper
https://doi.org/10.22002/D1.1970DOIData
ORCID:
AuthorORCID
Castellanos, Jorge C.0000-0002-0103-6430
Clayton, Robert W.0000-0003-3323-3508
Additional Information:The copyright holder for this preprint is the author/funder. We gratefully acknowledge NodalSeismic and Signal Hill Petroleum for allowing us to use the Long Beach and Extended Long Beach data, and LA seismic for the use of the Seal Beach data. Permission form these organizations is required to access the data. We thank Dan Hollis and Eric Campbell for facilitating the use of the seismic data. We extend our acknowledgement to Dan Gish and Steve Boljen for providing us with the migrated seismic sections of the Seal Beach survey. We also thank Michael Afanasiev and the Mondaic team for their help in setting up the numeric simulations. We are grateful to Zhe Jia for providing us with the ambient noise cross-correlations between the nodal instruments and the SCSN seismic station, and to Bruce Worden for providing us with the Vs30 measurements. The 3-D shear wave velocity model that is presented in this work can be downloaded from: https://doi.org/10.22002/D1.1970. This project was partially supported by NSF/EAER-1520081.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR-1520081
DOI:10.1002/essoar.10507964.2
Record Number:CaltechAUTHORS:20211012-211827814
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20211012-211827814
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111377
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:13 Oct 2021 17:19
Last Modified:13 Oct 2021 17:19

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